1985 K5 Blazer...left auto hub keeps engaging.

Makes noise like playing card in bicycle wheel spokes.

Will engage shifter to lock in hubs, then will release hubs and noise will temporarily go away only to start again.

Hub has been replaced with brand new one. Not an over grease problem. Shaft and joints seem OK, no excessive play.  Linkage readjusted to specs. Have removed transfer case and examined, replaced leaking seal, all checks out OK.

Anyone got a clue???    

I have found those hubs to be pretty trouble free. You do have to use very little gear with them though. Just enough to put a thin coating on parts.  

they have been fairly dependable for me in the past, although I don't like it when they unlock when ya back up, it can cause em to break the outer case if yer rough on em.

the most common problem had been the wire spring getting the ends broke off and the plastic cam getting ruined.

the card clicking is probably them not disengaging completely, sometimes cause by the tabbed lock ring not staying in place or the pin that holds it in place busted or incorrectly installed  

they have been fairly dependable for me in the past, although I don't like it when they unlock when ya back up, it can cause em to break the outer case if yer rough on em.

the most common problem had been the wire spring getting the ends broke off and the plastic cam getting ruined.

the card clicking is probably them not disengaging completely, sometimes cause by the tabbed lock ring not staying in place or the pin that holds it in place busted or incorrectly installed.

I've got a couple five gallon buckets full of auto hub parts and pieces if needed I could dig it out and get some pics of broken and good parts when I get some time....